Method of hot working localized portions of hollow metal articles



July 27, 1965 J. DITSON 3,196,534

METHOD OF HOT WOR G ALIZED PORTIONS OF HOLLOW META RTICLES Filed Nov. 20, 1963 2 Sheets-Sheet l HEATED PORTION 4 F/G 7 INVENTOR.

BY W win/wt ATTORNEY July 27, 1965 J, D. DITSON 3, 4

METHOD OF HOT WORKING LOCALIZED PORTIONS OF HOLLOW METAL ARTICLES Filed Nov. 20, 1963 2 Sheets-Sheet 2 INVENTOR.

J. D. 0/ TSON B QM 007W ATTORNEY United States Patent 3,196,534 METHOD OF HOT WORKING LGCALIZED PQR- TIONS 0F HQLLOW METAL ARTECLES J. D. Ditson, Asbury, N.J., assignor to Ingersoll-tand Company, New York, N.Y., a corporation of New Jersey Filed Nov. 20, N63, Ser. No. 325,020 4 Claims. (Cl. 29-423) This invention relates to the art of metal working. In particular, it concerns a process of hot working hollow metal articles.

During the manufacture of hollow metal articles, such as drill steels, it is frequently desirable to hot work a portion of the article after its hollow bore is formed. When the portion to be worked is locally heated, scale usually forms on the interior of the article and may be folded or embedded into the metal during the hot working process. This is undesirable because the scale causes a discontinuity in the metal structure which reduces its ability to survive fatigue. In the art, such discontinuities are known as stress raisers. This means that when loads are applied to the article, the resulting stress distributed throughout the structure of the article will be much higher in the vicinity of the discontinuities caused by the embedded scale. Such increased stress is more likely to initiate failures in the article starting at the discontinuities.

The principal object of this invention is to overcome and eliminate the scale formation problem previously associated with the hot working of portions of hollow metal articles.

Other important objects include the following: to provide a process wherein portions of hollow articles can be hot worked without the formation of scale on the interior of the article and the creation of discontinuities in the article as a result of the scale being embedded in the article during the hot working step; to provide an inexpensive and easily performed expedient for preventingthe formation of scale in a hollow metal article when it is being heated; and to provide an improved method of manufacturing drill steels.

These objects are generally attained by depositing a mass of vaporizing material within the hollow metal article at a distance from the locally heated portion of the article where the material is mildly heated enough to vaporize and drive out or otherwise eliminate the oxygen from the cavity of the article. Enough material is deposited to prevent scale from forming in the hollow article during the entire period that it is heated. If any of the material remains in the article after the completion of the process, it can be emptied from the article by various means depending on the character of the specific material used.

The invention is illustrated in the accompanying drawings wherein:

FIG. 1 is an axial section of a portion of an elongate hollow drill steel diagrammatically illustrating an embodiment of the invention wherein a plug of vapor-forming material is located in the hollow bore of the drill steel at a point remote from the portion being heated;

FIG. 2 is an axial section showing the drill steel of FIG. 1 after it is heated and at the beginning of the hot working step;

FIG. 3 is a similar section showing the drill steel during the hot working step;

FIG. 4 is a similar section showing the drill steel at the end of the hot working step;

FIG. 5 is an axial section of a drill steel illustrating another embodiment of the process; I

FIG. 6 is an elevational and partly diagrammatic view illustrating one way of depositing vaporizing material in the drill steel shown in FIG. 5; and

FIG. 7 is an axial section of a drill steel illustrating a third embodiment.

The drill steel 1 illustrated in FIG. 1 has a hollow bore 2 and an end 3. In effect, at this stage of the process, the drill steel 1 is nothing more than a thick walled tube. The drill steel 1 includes a portion 4 which is to be locally heated and hot worked.

A plug 5 of vaporizing material is mounted in the bore 2 at a point remote from the portion 4 which is to be heated for hot working. The plug 5 is spaced from the portion 4 far enough to be slowly vaporized by the heat thermally conducted through the metal from the heated portion 4. This distance will depend on factors such as the temperature of the heated portion 4, the temperature and rate of vaporization of the plug 5 and the amount of time which the plug 5 should last before being consumed. Materials suitable for the plug 5 may be a wax, such as parafiin wax.

FIG. 1 shows the portion 4 being locally heated by an induction coil 8. Although the use of induction heat is illustrated, other methods can be used. As the portion 4 is heated to a hot working temperature, say 2,000 degrees 5., heat is conducted along the remainder of the drill steel 1 to heat the plug 5 to a much lower temperature so that it begins vaporizing. Generally, it will take about one minute for the portion 4 to reach the hot working temperature using induction heat. If the plug 5 is wax, it will melt and vaporize at temperatures of 150-200 degrees F. This vapor travels along the bore 2 through the portion 4 and forces air and oxygen from the bore 2. In addition to displacing the oxygen and air from the bore 2, the vapor may also chemically combine with the oxygen, depending on the character of the vapor. For example, if the vapor is combustible, it may diffuse or mix with the oxygen and ignite, thus eliminating the oxygen from the bore 2. Eliminating oxygen from the bore 2 prevents scale from forming by oxidation on the interior surface of the bore.

After the drill steel 1 is sufficiently heated, the portion 4 is hot worked. FIG. 2 illustrates the portion 4 being placed between a pair of mating dies 10 and 11. The dies 10 and 11 are mounted in a press (not shown) so that they are relatively movable toward and away from each other. The dies 16 and 11 cooperate to form an annular cavity 12 surrounding the portion 4.

As the dies 10 and 11 come together on the portion 4, a plunger 13 having a reduced diameter pin 14 is moved axially toward the end 3 of the portion 4. The pin 14 is inserted into the bore 2 and the shoulder 15 of the plunger 13 engages the end 3. As the plunger 13 is forced against the end 3, the hot metal is forced to flow outward into the cavity 12 of the dies 10 and 11. This step is illustrated in FIG. 3. It should be noted that the dies 10 and 11 have two outer end portions 16 and 17 which closely surround the drill steel 1 and that the portion 16 tightly grips the steel 1 while the portion 17 loosely holds the drill steel so that the metal can flow along its surface.

After the cavity 12 is filled, the dies 10 and 11 are opened and the plunger 13 is retracted, as shown in FIG. 4. Thereafter. the drill steel 1 is Withdrawn from the dies 10 and 11 and allowed to cool. The plug 5 continues to vaporize throughout the period that the portion 4 is heated whereby scale is prevented from forming in the bore 2.

After the drill steel 1 is cooled below a scale-forming temperature, the remainder of the plug 5 can be melted from it by gently warming the portion of the drill steel immediately surrounding the plug 5, assuming that the plug 5 is composed of a material such as parafiin. Other methods may have to be used to empty the drill steel 1 when materials are used for the plug 5 which cannot be removed by heat. In many'cases, it may not be necessary to empty the drill steel of the remainder of the plug 5. This would he the case whereany remains of the plug 5 would not interfere with the use of the drill steel, 'or where such remains would automatically be elimi nated from the drill steel 1 during its initial use 7 The result provided by the embodiment of FIGS. 1 to 4 can also be substantially provided by entirely filling the bore 2 of the drill steel 1 with vaporizing material as shown in FIG. 5.

The material 18 should extend from. the end 3 far enough so that some of the material 13 will I remain in the bore 2 throughout the hot'working process} .As the portion 4 of the drill steel is locally heated, the

container 19 to a molten condition and an end portion of the drill steel 1 is dipped into the container 19.

FIG. 7 illustrates a third embodiment which provides about the same results that 'are' provided by the earlier described embodiments. In FIG. 7,,the interior'of the bore 2 is coated or lined with vaporizing material 29. The coating Ztl acts in about the same way as in the FIG. 5 embodiment.

ing 24) vaporizes and eliminates "oxygen from the bore 2 during the period thatflthe drill steel l isheatedto a scalef.

forming temperature. 1

As the portion 4 is heated, the. coating 20 within the limits of th'e portion 4 is melted" and eliminated. Thereafter, the remainder .ofithe coat- It appears that a variety of materials can be .used in the drill steel 1 to eliminate the formation of scale during the metal working operation. For example, in addition to wax such as parafiin, one can use heavy oil,

grease and certain paints or coatings having a carbonaceous composition. The material should either consume or expel the oxygen from the bore 2' and-provide a non-corrosive atmosphere in the bore. stances thatprovide'these characteristics can be used'for performing the foregoing method. f V

Generally, sub- 7 Although preferred embodiments of the invention are illustrated and described in detail, it'willbe understood that the invention is notlimited simply to these embodiments, but contemplates other embodiments and variations which utilize the concepts and teachings of this invention. V v 7 Having described my invention, I claim:

1. A process of hot working a portion of 'a hollow .met'al article comprising: depositing amass of material within the article whichis capable of being vaporized by heat at a temperature required for hot working the hollow metal article, at least some of said material being deposited in said article at a loc'ationremote from the portion of the article to which local heat is to be applied wherein the material will be heated slowly'enough to continue vaporizing and bathing the interior of the portion being heated with vapors which will prevent scale from forming therein during the later hot work-ing step; applying'heat to the portion of the article sufficient to raise its temperature to the required hot working temperature; and-hotworking the heated portion while said material vaporizesand prevents scale from. forming in said article while it is heated.

I ZxThB process of claim 1 wherein said material is a wax.

. 3. The process of claim 1 wherein thehollow article is filled with the material and the, material in the heated portion of the article i-seliminated :from the article by the local heat prior to the hot working step.

4. The process of claim 1 wherein the interior of the article is lined with the material which later vaporizes.

References Cited by the Examiner v UNITED STATES. PATENTS 1,428,148' 9/2 2 De c w; 252-29 2,588,625. 3/52 Fenian; 117 49 12,59o,4s1 3/52 Perry 252-56 2,821,016 *1/58 Dickson 29-424 Winn/roan A. WILTZ, Primary Examiner.

ZTHQMAS H. EAGER, Examiner. 

1. A PROCESS OF HOT WORKING A PORTION OF A HOLLOW METAL ARTICLE COMPRISING: DEPOSITING A MASS OF MATERIAL WITHIN THE ARTICLE WHICH IS CAPABLE OF BEING VAPORIZED BY HEAT AT A TEMPERATURE REQUIRED FOR HOT WORKING THE HOLLOW METAL ARTICLE, AT LEAST SOME OF SAID MATERIAL BEING DEPOSITED IN SAID ARTICLE AT A LOCATION REMOTE FROM THE PORTION OF THE ARTICLE TO WHICH LOCAL HEAT IS TO BE APPLIED WHEREIN THE MATERIAL WILL BE HEATED SLOWLY ENOUGH TO CONTINUE VAPORIZING AND BATHING THE INTERIOR OF THE PORTION BEING HEATED WITH VAPORS WHICH WILL PREVENT SCALE FROM FORMING THEREIN DURING THE LATER HOT WORKING STEP; APPLYING HEAT TO THE PORTION OF THE ARTICLE SUFFICIENT TO RAISE ITS TEMPERATURE TO THE REQUIRED HOT WORKING TEMPERATURE; AND HOT WORKING THE HEATED PORTION WHILE SAID MATERIAL VAPORIZES AND PREVENTS SCALE FROM FORMING IN SAID ARTICLE WHILE IT IS HEATED. 